Display device and method for manufacturing display device

ABSTRACT

According to one embodiment, a first substrate includes a first area, a second area, a third area, a fourth area and a fifth area in a planar view. In the first substrate, an organic insulating film is present in the second and the third areas, is present neither in the third area nor in the fifth area, and forms an adjustment area. A conductive film is provided on the organic insulating film, the third area, the fourth area and a part of the fifth area. A sealing material is present in a part of the second area, the third area, the fourth area and a part of the fifth area to attach the first substrate and a second substrate. A through hole penetrates the first and the second substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 15/441,955filed Feb. 24, 2017, and is based upon and claims the benefit ofpriority from Japanese Patent Application No. 2016-033998, filed Feb.25, 2016, the entire contents of each of which are incorporated hereinby reference.

FIELD

Embodiments described herein relate generally to a display device and amethod for manufacturing a display device.

BACKGROUND

Recently, liquid crystal display panels have been used for wearabledevices, which are assumed to be worn by the user. Liquid crystaldisplay panels can display pictures, letters, drawings, figures, etc.Since the display content can be switched, liquid crystal display panelsare expected to be used in various ways as wearable devices. Normally, aliquid crystal display panel comprises a first substrate on which aplurality of pixel electrodes are arranged, a second substrate facingthe first substrate, and a liquid crystal layer interposed between thefirst substrate and the second substrate. The liquid crystal displaypanel further comprises an outer circumferential sealing material. Thesealing material integrates the substrates along the outercircumferential portions of the substrates and encapsulates the liquidcrystal.

The above wearable devices include a watch type integrated with a clockmechanism comprising a pointer. This device requires a through holewhich penetrates the liquid crystal display panel to allocate the axisof rotation of the pointer. To encapsulate the liquid crystal betweenthe substrates, an inner sealing material having a ring shape should beprovided around the through hole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a planar view schematically showing a first substrate of adisplay device according to one embodiment.

FIG. 1B schematically shows the structure of the cross-sectional surfaceof the display device according to the embodiment.

FIG. 2 includes a planar view showing the vicinity of the centralportion of the first substrate of the display device according to theembodiment, and a cross-sectional view taken along line C-A-B.

FIG. 3 is a cross-sectional view taken along line A-B shown in FIG. 2.

FIG. 4 is a cross-sectional view taken along line A-C shown in FIG. 2.

FIG. 5 includes a planar view showing the vicinity of the centralportion of a first substrate of a display device according to anotherembodiment, and its cross-sectional view.

FIG. 6 is a cross-sectional view taken along line A-D shown in FIG. 5.

FIG. 7 includes a planar view showing the vicinity of the centralportion of a first substrate of a display device according to anotherembodiment, and a cross-sectional view taken along line C-A-E.

FIG. 8 is shown for schematically explaining a process for manufacturingthe display device according to the present embodiment.

FIG. 9 includes a planar view and a cross-sectional view showing thevicinity of an inlet for a liquid crystal.

FIG. 10 shows the relationship between a polarizer and a reinforcingplate around a through hole in the display device according to thepresent embodiment.

DETAILED DESCRIPTION

To manufacture a wearable device, an outer sealing material and an innersealing material are applied to a first substrate. A second substrate isattached to the first substrate. A liquid crystal is injected.

Thus, the manufacturing process requires a step of applying the innersealing material around a small through hole so as to have a ring shape.In this step, an appropriate amount of sealing material needs to beapplied in a ring shape in advance in a circular pattern. When thesecond substrate is attached to the first substrate, the substrates arepressed. At this time, the line width of the inner sealing materialshould not exceed a predetermined width. However, when the sealingmaterial is unicursally applied in a ring shape, the sealing material isredundant in the connected portion to surely connect the start and theend of the application. In the conventional device, in many cases, theinner sealing material extends beyond the scope of the assumption whenthe second substrate is attached to the first substrate. As a result,the width of a light-shielding film has to be increased to shield thesealing material from light, in other words, such that the sealingmaterial is not exposed to outside. When the line width of the sealingmaterial is increased, a part of the sealing material is extended to adisplay area and disturbs display.

In consideration of the above problem, the embodiments described hereinaim to provide a display device and a method for manufacturing a displaydevice, preventing the extension of the line width of a sealing materialto the outer circumferential side, decreasing the width of alight-shielding film, and enhancing reliability of display in a displayarea.

In general, according to one embodiment, a display device comprises:

a first substrate comprising a first area, a second area, a third area,a fourth area and a fifth area from an end portion to an inner side in aplanar view;

an organic insulating film which is present in the second area and thefourth area, is present neither in the third area nor in the fifth area,and forms an adjustment area whose thickness changes in the fourth area;

a conductive film continuously formed on the organic insulating film ofthe second area, the third area, the organic insulating film of thefourth area and a part of the fifth area;

a second substrate facing the first substrate;

a sealing material which is present in a part of the second area, thethird area, the fourth area and a part of the fifth area, and is used toattach the first substrate and the second substrate; and

a through hole which is adjacent to an inner side of the fifth area andpenetrates the first substrate and the second substrate.

The embodiments will be specifically described below.

The disclosure is merely an example, and proper changes in keeping withthe spirit of the invention, which are easily conceivable by a person ofordinary skill in the art, come within the scope of the invention as amatter of course. In addition, in some cases, in order to make thedescription clearer, the widths, thicknesses, shapes, etc., of therespective parts are illustrated schematically in the drawings, ratherthan as an accurate representation of what is implemented. However, suchschematic illustration in no way restricts the interpretation of theinvention. In addition, in the specification and drawings, structuralelements which function in the same or a similar manner to thosedescribed in connection with preceding drawings are denoted by likereference numbers, detailed description thereof being omitted unlessnecessary.

A first embodiment is shown.

FIG. 1A is a planar view schematically showing the structure of a firstsubstrate SUB1 of a display device 100. FIG. 1B schematically shows thecross-sectional surface of the display device 100. The first substrateSUB1 (which may be called an array substrate) comprises, for example, aglass plate as the base plate, and a group of subpixels PX_G including aplurality of subpixels in a display area ARE2 on a side of the glassplate. As shown in FIG. 1B, the first substrate SUB1 is integrated witha second substrate SUB2 by sealing materials 10 and 11. A liquid crystallayer LQ is encapsulated between the first substrate SUB1 and the secondsubstrate SUB2. FIG. 1B schematically shows, on the liquid crystal layerside of the first substrate SUB1, a semiconductor layer 21 structuring agroup of subpixels, a pixel electrode layer 22 forming a pixelelectrode, and the layer of an alignment film 58 facing the liquidcrystal layer and defining the direction of alignment of the liquidcrystal. FIG. 1B schematically shows, on the second substrate SUB2, acolor filter layer COL_F, a common electrode COM, and the layer of analignment film 59 facing the liquid crystal layer and defining thedirection of alignment of the liquid crystal.

In FIG. 1A, the display device 100 is circular in a planar view(specifically, when viewed perpendicularly to the substrate surface).However, the display device 100 may be shaped in various ways. Forexample, the display device 100 may be rectangular, triangular orpolygonal. The present embodiment is a display device integrated with adevice having the axis of rotation, for example, a clock. Since thepresent embodiment is applied to a circular wearable device, the firstsubstrate SUB1 and the second substrate SUB2 are circular in a planarview. In the example of FIG. 1, sealing materials 10 and 11 have acircular ring shape in a planar view.

The display device 100 is explained with enlarged views of the vicinityof a through hole HOL. See FIG. 2 and FIG. 4. FIG. 2 includes a planarview showing the vicinity of the central portion of the first substrateSUB1, and a cross-sectional view taken along line C-A-B. FIG. 3 is across-sectional view taken along line A-B shown in FIG. 2. FIG. 4 is across-sectional view taken along line A-C shown in FIG. 2.

As shown in FIG. 2 and FIG. 4, in a planar view, the liquid crystallayer LQ side of the first substrate SUB1 comprises a first area ARE1,which is the border area shown in FIG. 1A, the second area ARE2, a thirdarea ARE3, a fourth area ARE4, a fifth area ARE5 and a sixth area ARE6from the end portion (the outer circumferential edge) to the inner side(the inner circumferential side). The through hole HOL (see FIG. 2) isprovided in the sixth area ARE6 such that the bearing of a pointer andthe axis of the bearing pass through the through hole HOL.

The second area ARE2 is provided from the outer circumferential side tothe inner circumferential side. A display area is set in the second areaARE2. As shown in FIG. 3, a semiconductor channel 51 is formed on aglass plate 31 in the display area. A drive switching element DSW forapplying drive potential to a pixel electrode 57 is formed by using thesemiconductor channel 51. In the present embodiment, a reflectivedisplay system (in other words, a system for reflecting outside light onthe pixel electrode and outputting the light to the second substrateside) is assumed. Thus, the pixel electrode 57 is formed of, forexample, silver. The drive switching element DSW comprises thesemiconductor channel 51, a gate electrode 52, a source electrode 53 anda drain electrode 54. The semiconductor channel 51 comprises a channelarea at the central position facing the gate electrode 52. The sourceelectrode 53 is connected to a source area on one side of the channelarea. The drain electrode 54 is connected to a drain area on the otherside. An insulating layer 41 provided between the gate electrode 52 andthe semiconductor channel 51 is a first insulating layer which coversthe layer of the semiconductor channel 51. An insulating layer 42 is asecond insulating layer which covers the layer of the gate electrode 52.The first insulating layer 41 and the second insulating layer 42 extendto the vicinity of the inner circumferential end portion of the secondarea ARE2 as an insulating layer 23 shown in FIG. 2.

In the actual device, a plurality of drive switching elements DSWcorresponding to a plurality of subpixels are arrayed in atwo-dimensional manner inside the first substrate SUB1. However, as arepresentative of the drive switching elements DSW, FIG. 3 shows onlyone drive switching element DSW. In the present embodiment, a memorytype liquid crystal (memory-in-pixel [MIP]) display system is employed.Thus, a memory for retaining data 1 or 0 is provided so as to correspondto each subpixel. Although not shown in the drawings, for example, aswitching element for structuring the memory and a write switchingelement for writing data from a data line to the memory are provided.

The source electrode 53 and the drain electrode 54 are formed of, forexample, metal such as aluminum. The gate electrode 52 is connected to ascanning signal line (not shown) formed on the first insulating layer41. The source electrode 53 is connected to a video signal line (notshown) formed on the second insulating layer 42.

Organic insulating films 61 a and 61 b are formed on the semiconductorlayer 21. Organic insulating film 61 a is formed at least in the secondarea ARE2. Organic insulating film 61 a serves to planarize the asperityof the semiconductor layer 21. Thus, organic insulating film 61 a may becalled a first planarization film 61 a. The inner circumferential sideof the first planarization film 61 a extends to the extent that theinner circumferential edge of the insulating layer 23 is covered (seeFIG. 2 and FIG. 3). When the first planarization film 61 a is formed,the second planarization film (organic insulating film) 61 b is alsoformed in the fourth area ARE4.

The second planarization film 61 b basically forms a bank portion havinga ring shape. However, the second planarization film 61 b has apatterning having a slit (which may be called an adjustment area, adivided area or a gap portion) ARE4_s1 in a part of the secondplanarization film 61 b (see FIG. 2). Organic insulating film(planarization film) 61 b of the fourth area ARE4 comprises theadjustment area ARE4_s1 thinner than the other areas at least in a partof organic insulating film 61 b. The reasons for providing theadjustment area ARE4_s1 are explained below. In FIG. 2, only oneadjustment area ARE4_s1 is shown. However, more than one adjustment areaARE4_s1 may be provided.

On the first planarization film 61 a, the pixel electrode 57 is providedso as to correspond to the drive switching element DSW. The pixelelectrode 57 and the drain electrode 54 of the drive switching elementDSW are connected to each other by metal formed in a contact hole, forexample, indium tin oxide (ITO) 56 (connective metal or a conductivefilm) having transparency. The contact hole is formed in the firstplanarization film 61 a.

In many cases, the subpixels on the innermost circumferential side ofthe second area ARE2 are structured as dummy subpixels. When thesubpixels are dummy subpixels, the drive switching elements DSW aremaintained so as to be always in an off-state. Thus, the actual drivingis not performed. The ITO (connective metal or conductive film) 56structuring a part of each dummy subpixel is formed so as to extend tothe third area ARE3, the fourth area ARE4 and a part of the fifth areaARE5 after the planarization film 61 is formed.

Further, alignment film 58 is formed over the entire surfaces of the ITO56 and the pixel electrode 57. Alignment film 58 may be formed in therange of the second area ARE2.

The first substrate SUB1 is attached to the second substrate SUB2. Inthis case, as shown in FIG. 1A, FIG. 1B and FIG. 3, sealing materials 10and 11 are applied to the first substrate SUB1. In particular, theapplication state of the inner circumferential sealing material 11 is asshown in FIG. 3 and FIG. 4. Specifically, sealing material 11 is appliedto a part of the inner circumferential side of the second area ARE2, thethird area ARE3, the fourth area ARE4 and a part of the outercircumferential side of the fifth area ARE5. For example, sealingmaterial 11 is applied in the direction of arrow 11A shown in FIG. 2while sealing material 11 is extruded in a circular pattern from adevice for applying a sealing material. When sealing material 11 isapplied so as to have a ring shape in this manner, the adjustment areaARE4_s1 is selected as the start and end positions of the application.Thus, the adjustment area ARE4_s1 functions as a buffer portion whichabsorbs the excessive sealing material applied. In particular, at thestart position (that is, the end position) for forming a circle inconnection with the application of the sealing material, the applicationareas of sealing material 11 overlap each other. Thus, the amount ofsealing material is greater than that in the other application areas.This excessive sealing material can be absorbed by the adjustment areaARE4_s1 (see FIG. 4 and FIG. 2).

In this way, it is possible to prevent increase in the line width ofsealing material 11. As a result, the extension of a part of the sealingmaterial to the display area can be prevented. Thus, display is notdisturbed. Further, the width of a light-shielding film can be reduced.

In the above liquid crystal display panel 100, the subpixel includingthe pixel electrode 57 is driven in the following manner. When a drivesignal (video signal) is supplied to the pixel electrode 57 via thedrive switching element DSW comprising the semiconductor channel 51, anelectric field is generated between the common electrode COM formed onthe second substrate SUB2 and the pixel electrode 57. Thus, the liquidcrystal is driven, thereby realizing a phototransmissive state. In thismanner, the light entering from the outside on the second substrate SUB2side is reflected on the pixel electrode 57. The reflected light can bevisually recognized.

A polarizer is attached to the upper surface of the glass plate of thesecond substrate SUB2. A reinforcing plate is also attached to thevicinity of the through hole HOL of the second substrate SUB2. The holeof the polarizer is preferably greater than the through hole HOL. Whenthe hole of the polarizer is greater than the through hole HOL, thelight-shielding film may be exposed only on the innermost side. However,this exposure can be prevented by providing the inner end of thereinforcing plate so as to be on the inner side in comparison with theinner end of the hole of the polarizer. The reinforcing plate may beprovided either on the polarizer or in the same layer as the polarizer.The light-shielding film provided around the through hole HOL on theliquid crystal layer side of the second substrate SUB2 overlaps at leastthe third area and the fourth area in a planar view. The light-shieldingfilm may at least partially overlap the second area, the third area, thefourth area and the fifth area. The relationship between the polarizerand the reinforcing plate is explained later.

In the above display device, alignment film 58 is provided insidesealing material 11 on the inner circumferential (central) side. The ITO56 is provided under alignment film 58. In the manufacturing process,alignment film 58 is printed on the ITO, which is metal oxide. Sincealignment film 58 has a good affinity for the ITO, the process is easy.Moreover, the adhesiveness to the substrate and the organic film isimproved by providing the ITO. In this way, it is possible to preventmoisture intrusion from outside.

When the first substrate SUB1 and the second substrate SUB2 areconcentrically attached to each other by sealing materials 10 and 11,the first substrate SUB1 and the second substrate SUB2 are integrated.At this time, an inlet for injecting a liquid crystal into the spacebetween the first substrate SUB1 and the second substrate SUB2 isprovided in, for example, sealing material 10. After sealing materials10 and 11 are cured, and thus, the first substrate SUB1 and the secondsubstrate SUB2 are integrated, the through hole HOL (corresponding tothe central axis of the ring formed by sealing material 11) whichpenetrates the first substrate SUB1 and the second substrate SUB2 isprovided. The through hole HOL is the sixth area ARE6 surrounded by thefifth area ARE5. The through hole HOL is formed by using, for example,laser light, so as to be greater than the bearing of the pointer of theclock mechanism incorporated into the liquid crystal panel.Subsequently, a liquid crystal is injected through the inlet. The inletis sealed. The process for injecting a liquid crystal is performed afterthe process for making the through hole HOL to prevent the heat orimpact of the hole-making process from detrimentally affecting theliquid crystal.

FIG. 5 and FIG. 6 show a second embodiment. The same structures as FIG.1 to FIG. 4 are denoted by the same reference numbers as FIG. 1 to FIG.4. FIG. 5 includes a planar view showing the vicinity of the centralportion of a first substrate, and a corresponding cross-sectional view.FIG. 6 is a cross-sectional view taken along line A-D shown in FIG. 5.

The embodiment shown in FIG. 5 and FIG. 6 is different from theaforementioned embodiment in terms of the shape of a secondplanarization film 61 b formed in a fourth area ARE4. In a planar view,the second planarization film 61 b has a ring shape. In across-sectional view, the second planarization film 61 b comprises a lowstep portion (adjustment area) ARE4_s2 on the inner side. The height ofthe step portion (adjustment area) ARE4_s2 is preferably greater than orequal to thirty percent and less than or equal to eighty percent of thatof the highest portion of the second planarization film 61 b.

In the example of FIG. 5 and FIG. 6, the cross-sectional shape of thesecond planarization film 61 b is stepwise. However, the secondplanarization film 61 b may be formed such that the inclined surface isgradually lower toward the inner side.

When the second planarization film 61 b comprises the adjustment areaARE_s2, the following effect can be obtained.

It is assumed that a sealing material 11 is excessively applied to theoverlapping area of the start and end positions when sealing material 11is drawn on the second planarization film 61 b so as to have a ringshape. Even in this case, sealing material 11 flows to the inner side(the through hole HOL side) by the step or inclination of the secondplanarization film 61 b. This structure prevents the line of sealingmaterial 11 from widening to the second area ARE2 side. As a result, thesealing material does not extend to the display area. In this way,display is not affected by the extension of the sealing material.Moreover, the width of a light-shielding film can be reduced.

FIG. 7 shows a third embodiment. The same structures as FIG. 1 to FIG. 6are denoted by the same reference numbers as FIG. 1 to FIG. 6. FIG. 7includes a planar view showing the vicinity of the central portion of afirst substrate, and a corresponding cross-sectional view. The thirdembodiment comprises both the structure of the embodiment shown in FIG.1 to FIG. 4 and the structure of the embodiment shown in FIG. 5 and FIG.6.

A fourth area ARE4 comprises a second planarization film 61 b. Thesecond planarization film 61 b comprises both an adjustment area ARE4_s1and an adjustment area ARE4_s2. The same effects as the aforementionedembodiments can be obtained from the third embodiment.

FIG. 8 is a process explanatory diagram schematically showing a processfor manufacturing the display device of each of the above embodiments.After the semiconductor layer 21 is formed with respect to the firstsubstrate SUB1 (process PS1), organic films (specifically, the firstplanarization film and the second planarization film) are formed(process PS2). When the second planarization film is formed, theadjustment area(s) shown in FIG. 2, FIG. 5 or FIG. 7 is (are) selected.

After the planarization films are formed, ITO and a pixel electrode areformed (process PS3). Subsequently, an alignment film is formed (processPS4). After the alignment film is formed, sealing materials are applied.Subsequently, the first substrate is attached to the second substrate(processes PS5 and PS6). Subsequently, chemical etching is applied withhydrofluoric acid to the glass plates of the first and second substratessuch that the glass plates are thin (process PS7). Subsequently, thethrough hole HOL for attaching the pointer is formed using laser light(process PS8).

A liquid crystal is injected through the inlet provided in a part of thesealing material. After the injection, the inlet is closed (processPS9). A polarizer is attached to the external side of the secondsubstrate SUB2. Subsequently, a reinforcing plate is attached to theupper surface of the polarizer (process SP10). By the above procedure,the trace of the inlet remains in the display device after the liquidcrystal is encapsulated. For example, a sealant remains after the inletis closed.

FIG. 9(a) is a planar view showing an inlet 70 formed to inject a liquidcrystal. FIG. 9(b) is a cross-sectional view taken along line X-Y. Whenthe first substrate SUB1 is attached to the second substrate SUB2, theinlet 70 is formed in a part of sealing material 10. In other words, inthe middle of application of sealing material 10 into a ring shape, thesealing material is disconnected to form the inlet 70. In the inlet 70,a planarization film 82 formed on the glass plate 81 of the secondsubstrate SUB2 faces the planarization film 61 (61 a) formed on theglass plate 31 of the first substrate SUB1. Spacers 83 a, 83 b and 83 care provided on the planarization film 82 of the second substrate SUB2to maintain the strength. The inlet 70 is sealed by sealant 10A afterthe liquid crystal is injected.

FIG. 10 shows the positional relationships between the members formed onthe glass plate 81 of the second substrate SUB2 and the members formedon the first substrate SUB1 around the through hole HOL. Alight-shielding film BM is formed on the liquid crystal layer LQ side ofthe glass plate 81. A polarizer 91 is attached to the external side ofthe glass plate 81 (in other words, to the side opposite to the liquidcrystal layer). Moreover, a reinforcing plate 92 is attached to theupper surface of the polarizer 91. In a planar view, the light-shieldingfilm BM provided near the through hole HOL overlaps at least the secondarea and the third area. The light-shielding film BM may at leastpartially overlap the first area, the second area, the third area andthe fourth area. Near the through hole HOL, the inner circumferentialedge of the reinforcing plate 92 is closer to the through hole HOL thanthe inner circumferential edge of the polarizer 91. The liquid crystallayer LQ is located between the first substrate SUB1 and the secondsubstrate SUB2. The polarizer 91 is provided on a side of the secondsubstrate SUB2 so as to be opposite to the liquid crystal layer LQ.Moreover, the reinforcing plate 92 is provided on the upper surface ofthe polarizer 91. Around the through hole HOL, the radius of the innercircumferential edge of the polarizer 91 is greater than that of thereinforcing plate 92. This structure prevents the exposure of thelight-shielding film BM on the inner circumferential side to outsidethrough the reinforcing plate 92. When the polarizer 92 extends to theinner circumferential side, the light-shielding film BM is exposed tooutside through the polarizer 92. However, the exposure of thelight-shielding film BM to outside is prevented by the above structure.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A liquid crystal display device comprising: afirst substrate; a second substrate; a liquid crystal layer; an outersealing material and an inner sealing material for holding the liquidcrystal layer between the first substrate and the second substrate; anda through hole which penetrates the first substrate and the secondsubstrate on an inner side in comparison with the inner sealingmaterial, wherein the first substrate comprises an organic insulatinglayer, and the organic insulating layer comprises, in an areaoverlapping the inner sealing material, a groove portion along thethrough hole, and a bank portion formed on the inner side in comparisonwith the groove portion.
 2. The liquid crystal display device of claim1, wherein the bank portion comprises a gap portion connecting thegroove portion and the through hole.
 3. The liquid crystal displaydevice of claim 1, wherein the bank portion comprises a step portionlower than the bank portion on a surface on a through hole side.
 4. Theliquid crystal display device of claim 1, wherein the bank portioncomprises an inclined portion on a surface on a through hole side.